Ebola could have "significant economic" ramifcations for a number of west African countries, a report from ratings agency Moody's has warned.

More than 1,200 people have died since February in the outbreak of the tropical virus.

As the human cost continues to rise and west African governments and global healthcare organisations try to fight the spread of the disease, Moody's has raised concerns about the wider economic threat of the epidemic.

Combined with increased spending on treating the outbreak, the agency predicts the pressure on government budgets could jeopardise economic growth across the region.

Nigeria, which has declared a state of emergency, is the largest oil producer on the continent and the twelfth-largest producer in the world, with international companies such as Exxon, Chevron, Shell, ENI and Total operating there.

Matt Robinson, senior credit officer at Moody's in London, who wrote the report, warned: "If a significant outbreak emerges in the Nigerian capital of Lagos, the consequences for the West African oil and gas industry would be considerable.

"Any material decline in production would quickly translate into economic and fiscal deterioration."

Image Caption:Checkpoints have been set up in Liberia to check travellers

Moody’s expects commercial and transport disruptions in the wider west African region to last for at least the next month.

The Moody's report also expects ebola to have an impact on revenue generation in the region "where budgets are already hindered by low tax collection".

An assessment from the World Bank and International Monetary Fund in June predicted that GDP growth in Guinea, which on Thursday declared a public health emergency after more than 350 deaths there, will fall from 4.5% to 3.5% as a result of the epidemic.

In Liberia, where there are hopes that doctors diagnosed with the virus can start treatment with some of the limited supply of experimental drug ZMapp, the government said that ebola-related expenses in the second quarter reached $12m.

Sierra Leone, where there is also a national emergency, is extremely reliant on its mining sector. Should ebola have an impact on production, Moody's has said GDP growth could fall from the 16% recorded in 2013.

The report comes as the World Health Organisation (WHO) classified Kenya, in east Africa, as a "high-risk" country for the spread of the virus due to its transport links with west Africa.

People have been urged to avoid non-essential travel to the affected areas, and British Airways and Emirates are among the international airlines to have suspended flights in the region.

Ebola has a case fatality rate of up to 90% and severely ill patients require intensive supportive care. No vaccine is available for use.